Clinical Research Directory

Vitamin B12: a Biological Marker of Systemic Disease or Infection Flare-up in Patients Treated with Tocilizumab?

Tocilizumab is a monoclonal antibody that acts as an IL-6 receptor antagonist It is responsible for a reduction in the hepatic synthesis of inflammatory proteins, including CRP (C-reactive protein). Thus, the diagnosis of a relapse of the autoimmune or auto inflammatory disease (AI/ID) or an infection is made difficult in patients treated with tocilizumab and there is to date no marker of inflammation validated in patients receiving tocilizumab. Vitamin B12 is an essential element that participates to haematopoiesis, myelin integrity, neuronal function and DNA synthesis. Vitamin B12 is carried by haptocorrin and transcobalamin II (TCII). Vitamin B12 increases in many pathological situations, including infections and AI/ID due to the increase of its transport proteins elevation (mostly transcobalamin II). The sponsor did not find any study in the literature studying the level of vitamin B12 or TCII in patients taking tocilizumab. The sponsor also did not find any physiopathological argument in favor of an inhibition of TCII synthesis by tocilizumab. As such, TCII dosage could be of interest, but the dosage is not available in routine whereas vitamin B12 dosage is available in every laboratory and is four times cheaper.